In general, one provides a closure with tamper-evident capability by forming the skirt of the closure with a score line so as to define a removable marginal edge portion of the skirt as a security ring or band. The security ring can have a snap-engagement construction, which enables it to make a locking engagement with a bead of the container, so that when the closure is removed it severs along the score line, leaving the security band loose on the container clearly indicating that the closure has been removed, once the closure has been reapplied to the container.
When formed in plastics material the score line may be provided by a peripheral slit connected by a bridge of plastic material which is capable of tearing when the closure is first opened. Thus, the score line comprises about ten or more frangible bridges of small cross-sectional area which are spaced around the closure and separated by slits at which the plastics material of the skirt is severed completely through its thickness.
There are two methods for the formation of the score line in a plastics skirt. In one method the score line is molded into the skirt. However, such molding of the score line often requires complicated tool parts which are expensive.
The second method for forming the score line avoids the particular shortcomings of the first method. In this second method the score line is formed after the closure has been molded, usually by means of a knife to which the closure is presented. The knife must penetrate through the wall of the closure skirt to form the slits, and the skirt is support internally by a roller or other support member which is inserted into it.
One manner of using a knife to cut the slit is to insert a mandrel into the underside of the cap and bear against the tabs which have been folded against the inner side wall of the closure and rotating the cap through rotation of the mandrel. The knife is reciprocating and cuts spaced slits in the closure skirt with frangible bridges in between. However, the hold of the mandrel on the closure wall is not absolute and occasionally slips occur, causing irregular cutting of the slits in the tamper-evident band. Further the knife can and does cut into the tabs which provide support for the skirt wall during the cutting operation.
Therefore a benefit of the subject invention is a method and apparatus by which consistently spaced slits may be cut into a closure skirt, without harming the tabs.